1. Field of the Invention
The present invention relates generally to an outboard motor, and more particularly relates to an outboard motor having a cowling which encloses an engine.
2. Description of Related Art
Typically, outboard motors are mounted on a transom board of an associated watercraft. Such an outboard motor usually has an engine for powering a propulsion device such as, for example, a propeller that generates thrust force of the watercraft. A cowling typically defines an engine compartment that surrounds the engine for protecting the engine.
The cowling typically includes a structure for allowing outside air to enter the engine compartment to provide intake air for the engine. The cowling preferably is configured to block most or all splashing water from entering the engine compartment through the air intake structure, but allows air to enter. In one prior structure, the air intake structure includes an air duct that extends upward from a top surface of the cowling. A cover member extends over the air duct member so as to form a space between the cowling and the cover. Ambient air can enter the space from which the air duct conducts such air into the engine compartment. However, since the air duct extends upwardly from the cowling surface, water that may enter the space is blocked from flowing through the air duct. See, for example, Japanese Patent No. 3046391.
Outboard motors typically include an internal combustion engine that generates significant heat during operation. As can be appreciated, this heat can warm up the air within the engine compartment. Further, traditionally, outboard motor cowlings are made of a synthetic resin that is not very heat conductive. As such, heat from the engine is generally not transferred to the cowling, and instead is radiated to the air. Hot engine intake air can result in a decline of engine charging efficiency.
In order to expedite the radiation of the heat through the cowling, Japanese Patent Publication No. P2004-299485A discloses a cowling made of nonferrous metal. Some cowlings disclosed in this publication have an air duct member and top cover portion of the body of the cowling. Although the radiation of heat can be greatly improved, the cowling can be heavier than a conventional resin-based cowling.